Prior to commencing operations in the area the pilot carried out an aerial reconnaissance to check the location of powerlines. He stated that he had almost completed the second load when he had the feeling that he was running out of chemical. He believes that he momentarily looked at his instruments to check for pressure and load remaining and temporily forgot about the presence of the powerlines. He subsequently saw the powerlines as the aircraft was approaching the end of the run, just before they were struck by the canopy of the helicopter. Control was maintained with difficulty, and when the pilot noticed that the aircraft was trailing wires he decided to land. The landing in a cleared paddock was heavy, causing the skids to collapse, and the main rotor to flex downwards, striking the tailboom and severing the tail rotor. The pilot stated that the powerlines were difficult to see because of wire sag and the backdrop of trees and buildings. This accident was not the subject of an on-site investigation.

Because of deteriorating lift conditions, the pilot elected to make an outlanding. The paddock selected had been recently ploughed and the surface was soft. Almost immediately after touchdown the glider yawed, then groundlooped through 90 degrees, resulting in a compression fracture of the fuselage. It was likely that the glider had been affected by a sudden wind gust shortly after touchdown, and the pilot had been unable to maintain directional control.

The pilot was making a landing approach in moderate crosswind conditions. Touch-down was made in a three-point attitude at an airspeed of about 40 knots. Immediately afterwards, the pilot experienced difficulty in preventing the into-wind wing from rising. He elected to go around and applied full throttle, but was unable to maintain directional control. The propeller struck the ground and the aircraft cartwheeled before coming to rest. Recorded aerodrome information received by the pilot indicated that the surface wind was gusting above the aircraft maximum demonstrated crosswind component. On final approach, the pilot became aware that a significant crosswind existed, but he continued the approach, using a short field landing technique. When directional control was lost after touchdown and a go around was attempted, the combination of an uncontrolled turn downwind, the low airspeed and a gusty wind caused the aircraft to stall.

The pilot reported that a power loss occurred as the aircraft climbed through an altitude of about 35 feet. The subsequent forced landing was made onto newly cultivated ground, the skids dug in, and all four skid legs were bent. On exiting the aircraft, the pilot noted a strong smell of what he considered to be burnt clutch linings. An inspection of the aircraft revealed a worn clutch. Although the clutch was still within serviceability limits, it is considered possible that some slippage occurred which resulted in the loss of power to the rotor system. This accident was not the subject of an on-site investigation.

Circumstances:

The helicopter was operating onto a floating pontoon situated adjacent to a reef area. The pontoon was 30.65 m long and 9.32 m wide and consisted of a wooden platform mounted above two steel floats. A series of hardwood joists 295 mm x 85 mm and approx. 950 mm apart were mounted between the floats and 35 mm x 110 mm hardwood decking was nailed to the joists to form the platform surface. The decking ran lengthwise along the pontoon. The pontoon was constructed in 1985 and had been in operation almost continuously since then. While mainly skid equipped helicopters operated onto the pontoon, it had also been used by wheeled helicopters, including the Agusta 109. It was established that Agusta 109s had landed on the pontoon on some hundreds of occasions prior to the accident. Company pilots reported that they had observed decking planks bend when subjected to the weight of the Agusta 109 through its mainwheels. For this reason, the general practice for Agusta 109 operations onto the platform was for the mainwheels to be positioned over the joists when landing along the pontoon parallel to the decking. At the time of the accident, there was a northerly wind at about 15 kts and the pontoon was pitching some 25-30 cm in the swell. The northern end of the pontoon was occupied by another company helicopter which had just landed and was parked across the pontoon with its engine running and passengers still on board. VH-LHJ approached into wind to land along the pontoon. The helicopter was being flown by the pilot in the left seat. Shortly before the wheels contacted the decking, the pilot in the right seat opened his door to check the position of the mainwheels in relation to the joists. As the mainwheels touched the surface, he reported to the pilot flying the aircraft that the mainwheels were 6-8 in behind the beam. As the weight of the helicopter was transferred to the wheels, the right-seat pilot saw the decking beneath the right mainwheel flex slightly and then crack and break. The helicopter rolled rapidly to the right and the main rotor blades began impacting the pontoon and the water. The helicopter eventually came to rest on its right side, having veered about 130` to the right adjacent to the southern edge of the pontoon. The impact forces destroyed the main rotor blades, substantially damaged the rotor head, and broke the tail boom. There was no evidence of any fault in the helicopter which might have contributed to the accident. There was also no evidence of a hard landing or any other pilot-related aspect which might have caused excessive loads to be placed on the decking during the landing sequence. The investigation therefore focused on the pontoon itself, and a study was commissioned to examine the strength of the pontoon decking with respect to the helicopter types known to use the pontoon. The results of the evaluation of the pontoon decking were as follows 1. The condition of the decking timber was such that deterioration due to exposure to the elements was concluded not to have been a factor in the deck failure. 2. The failure of the decking when subjected to Agusta mainwheel loading was due to grossly excessive bending stress. The overload factor was calculated as 8.39 and readily explained the failure. The only pontoon design documentation which could be located concerned the general structure and dimensions of the pontoon and contained no details on deck strength considerations. No comment can be made, therefore, as to whether the wheel or skid loadings of the various helicopter types using the pontoon, and particularly those for the Agusta 109, were considered during the design of the pontoon.

Significant Factors:

The following factors were considered relevant to the development of the accident

1. The strength of the pontoon decking was inadequate for Agusta 109 operations.

2. The pontoon decking failed due to excessive bending stress when subjected to loading through the right mainwheel of the helicopter.

Recommendations:

The helicopter operator and the pontoon owner, along with the Civil Aviation Authority (CAA), were notified of the progress of the investigation. This included information contained in a preliminary report followed later by the complete testing details, technical analysis, and stress calculations concerning the pontoon decking. The analysis concluded that the strength of the decking was inadequate for all helicopter types which used the pontoon and steps were instituted by the operator and the pontoon owner for the deck to be strengthened.

1. A recommendation was made to the CAA on 13 September 1991 that the circumstances of the accident be brought to the attention of other organisations involved in operations on to helicopter landing sites with timber decking and that these organisations confirm the design specifications of those surfaces for the particular types of helicopter involved.

2. It is further recommended that the Civil Aviation Authority through surveillance, following the failure and subsequent repair of this pontoon, confirm that the pontoons and other helicopter landing sites which are being used by this operator, have the structural integrity to accommodate operations of the relevant helicopter types.

Circumstances:

The pilot had flown from Archerfield to Surfers Gardens to pick up a passenger and made a normal landing on strip 12. About 20 minutes later he was taxiing for take-off on strip 12 when the nosewheel strut collapsed, and the propeller struck the ground. The ALA had only recently been reopened after having been closed for some time due to a soft wet surface. The nosewheel had entered a slight depression prior to the strut collapsing but the depression should not have been sufficient to overload the strut to the point of failure at normal taxiing speed. Examination of the nose gear showed that the metal to metal epoxy bonding which attaches the torque tube to the airframe end fittings had failed. This failure allowed the torque tube to rotate inside the end fittings, to the extent that all normal suspension action was lost. The nose gear strut assembly then folded upwards into the engine cowls, and the propeller struck the ground. The epoxy bonding had deteriorated to the extent that the load carrying capacity of the nose gear had been substantially reduced.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. The nosewheel entered a depression whilst the aircraft was being taxied.
2. The epoxy glue which bonds the nose landing gear torque tube to the attachment fittings failed.

Recommendations:

The engineer involved in the recovery of the aircraft had previously experienced a similar failure on this type of aircraft. As a result, he had sought assistance from the American distributor. The distributor confirmed that as a result of many USA operators experiencing similar defects, a Supplemental Type Certificate (STC) number SA3564SW, had been issued allowing modification of the torque tube and end fittings. This simple modification places taper pins through the torque tube and end fittings, effectively preventing movement even if the epoxy bonding deteriorates. The Civil Aviation Authority should examine the above aspects with a view to recommending incorporation of a similar modification to all high-houred aircraft of this type.

Circumstances:

The aircraft had taken off on runway 24 towards a range of hills. Wind at the time was reported as a steady 20 knots from the south-west, straight down the runway. After take-off, the pilot retracted the landing gear and reduced power for climb. He reported that soon after, the aircraft encountered a windshear, lost airspeed, and failed to climb. He did not reapply full power. There were no clear areas ahead, so he commenced a left turn; however, the airspeed decayed further, and the left wing dropped. The aircraft struck the top branches of a 15 m pine tree, rolling inverted before coming to rest approximately 15 m from a house. The occupants were trapped in the wreckage until emergency services arrived. The accident site was approximately 1 250 m south-west of the end of the runway. The terrain is below a five percent gradient, but beyond this area it rises quite steeply to a ridge line approximately 5 km from the runway. No fault was found with the aircraft. There was evidence from propeller strike marks on severed branches that the engine had been delivering substantial power at the time of impact. The area is well known for local wind effects due to the terrain. The prevailing wind direction would have been conducive to wind shear in the lee of the ridge where the accident occurred. This is the second of three similar accidents which have occurred within an area of 1.5 km during the last few years. In each case the aircraft failed to outclimb the terrain after taking off from runway 24.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. The aircraft may have encountered windshear soon after lift-off.

2. The pilot did not operate the aircraft for maximum performance.

3. The pilot was not able to maintain speed.

Recommendations:

Over the past ten years BASI records indicate at least 16 take-off accidents to fixed wing aircraft attributed in part or totally to the effects of wind over the local terrain and to high density altitude. The following recommendations are made:

1. The CAA consider preparing an educational article to be widely distributed detailing considerations for GA type aircraft operations in areas where flight may be affected by terrain, wind, and density altitude.

2. The CAA bring to the attention of training schools the need to accent these issues in both theoretical and practical training.

Spraying operations were being conducted in generally calm weather conditions. One load had been sprayed successfully, but the pilot later advised that, as he manoeuvred at the end of the second run with the next load, sink was encountered. Although he dumped the remainder of the load, he reported that he had insufficient time to increase power. The aircraft collided with a tree, then struck the edge of a road and groundlooped into an adjacent crop. Weather conditions at the time were unlikely to have produced any sink. It was probable that while turning towards rising ground the pilot misjudged the slope of the terrain. The aircraft had stalled, with insufficient height available in which to effect a recovery.

The pilot was accompanied by two friends on a local flight to view a property in the South West Rocks area. About twenty minutes after take off, the engine commenced to run roughly and lose power. The pilot carried out a trouble check which revealed the left magneto had failed. Whilst the pilot was attempting a forced landing the engine stopped, the aircraft collided with trees before coming to rest in a semi-inverted attitude. The pilot and passengers were able to vacate the aircraft without assistance. Post accident testing of the ignition system revealed that both magnetos were unserviceable because of age deterioration of the insulation around the transformer coils. The failure of both magnetos resulted in the loss of engine power. A service bulletin was issued by the magneto manufacturer in 1973 which recommended replacement of the transformer coils in the type of magneto fitted to VH-DLT. The aircaft maintenance records show the magnetos were repaired and tested in 1985 but the transformer coils were not replaced as recommended by the service bulletin.

The pilot was cleared to conduct a straight in approach at the destination aerodrome. At a position 15 kilometres from touchdown, he commenced the prelanding checks and selected gear down. The gear selector panel indication of three green lights and a visual inspection from the cockpit windows, which included the use of an engine cowl mounted mirror to view the nose landing gear, confirmed that the landing gear was fully extended. Shortly after touchdown, the right main gear collapsed causing the aircraft to veer from the runway. An inspection of the gear and its systems revealed two defects which are considered to have contributed to this accident. The throttle warning horn had been rendered unserviceable due to a blown fuse in the warning system electrical circuit. The down-lock pin had failed to locate in the lower dragstay due to a worn bearing, allowing the stay to be misaligned from the lock pin. The down-lock microswitch is attached to the lower dragstay and does not come into contact with the down-lock pin. It is therefore possible for the gear to be fully extended, the electrical circuit to be made and three greens indicating, but for the down-lock pin to be disengaged. It is considered that the gear extended fully prior to touchdown, providing the pilot with three green indications, but remained in an unlocked state due to the misalignment of the lock assembly. As the weight of the aircraft transferred onto the gear during the landing roll, the unlocked gear collapsed. The pilot was deprived of an aural warning, due to the failed aural warning electrical warning circuit. The investigation also revealed a potential problem with the main gear ground handling lock pin system, which is used to prevent the down-lock pin from dislocating. If the down-lock pin has not correctly located in the lower dragstay, the ground handling pin is ineffective. This accident was not the subject of an on-site investigation.